This invention relates to electrochemical generators such as galvanic primary and secondary batteries and fuel cells, and more particularly, to an improvement in such generators and in the method of using such generators which involves rotating the electrodes and other portions of the generator to provide a substantial centrifugal force and utilizing the centrifugal force to perform a variety of required generator functions.
Conventional electric batteries, such as the well-known lead acid battery, have both the electrodes and the electrolyte stationary with respect to the casing of the device. While such devies have been adequate for some applications, their energy density, defined as the total energy delivered by the battery system divided by the total weight of the system, has not been adequate for many applications and in particular as a power source for an electric car.
Batteries capable of generating much higher energy densities (in the order of two to ten times greater) include air-metal devices such as zinc-air and aluminum-air cells. However, a number of problems are encountered in connection with such devices which has limited their commercial potential. These problems include the need to circulate air past the air electrode requiring an external air pump. It is also necessary in these devices to circulate the electrolyte past the electrodes to inhibit dendrite formation during charging and to circulate crystallizing reaction products during discharge. This again requires some type of external pump, the air pump and the electrolyte pump adding to the overall weight of the system and thus reducing the energy density.
While circulating the electrolyte has reduced dendrite growth during recharging, it has by no means eliminated this problem, and it has not addressed the problem of uneven plating of the metal during recharge which tends to reduce the number of recharge cycles and therefore the useful life of the battery. In addition to the plating being uneven, the plated material is often spongy reducing the energy output of the device. Prior art devices which have used mechanical devices to shake, wipe or rub the electrode surfaces and/or have used one or more circular electrodes which are rotated about their center axis have also not completely solved these problems.
In addition, as the metal electrode is consumed during discharge, the spacing between the electrodes increases, reducing the efficiency and output of the generator. It is desirable to maintain this spacing uniform throughout the discharge cycle. Another problem with prior art generators of the metal air type is in preventing the electrolyte from flooding the pores of the gas electrode and in preventing reaction products from clogging these pores, the flooding or clogging of the pores inhibiting the flow of gas therethrough to the reaction zone. It has also been found that air electrodes can be destroyed in a relatively short time as a result anodic transfer combined with mechanical attacks caused by oxygen bubble formation during recharging of the battery. It is therefore desirable that electrolyte be kept out of contact with these electrodes during recharging. Other functions within the batteries which have required additional hardware in prior art batteries include draining of electrolyte for standstill periods, flushing of electrodes with water or neutralizing liquids for prolonged standstill periods and dispersing or removing oxygen and hydrogen bubbles from the electrolyte during operation. Separation and removal of reaction products from the electrolyte is still another problem which has required additional hardware in the prior art.